1. Field of the Invention
An aspect of the present invention relates to a bio cell cleaning centrifuge for cleaning bio cell such as red blood cell by centrifugal force, and particularly to a bio cell cleaning centrifuge which is suited to make a cleaning advantage large and make cleaning reliability high, and a bio cell cleaning rotor used in the same.
2. Description of the Related Art
Conventionally, a bio cell cleaning centrifuge (blood cell cleaning centrifuge) has been known, which is used, in an antiglobulin test in blood transfusion, a cross-matching test and irregular antibody screening, in order to remove unwanted antibody from a suspension by cleaning red blood cell with a cleaning liquid such as physiological saline.
The known bio cell cleaning centrifuge includes a motor having a drive shaft; a rotor which is coupled to the drive shaft of the motor and rotated by the motor; plural test tube holders which are attached onto the rotor in a circular array so as to be pivotally movable, and can pivotally move in a horizontal direction of the outside of the circular array upon application of centrifugal force generated by rotation of the rotor, and each of which is formed of a magnetic member; a cleaning liquid distributor which is attached to the rotor, rotates together with the rotor, and supplies cleaning liquid into plural test tubes respectively held by the plural test tube holders; and a magnetic element (locking mechanism) which attracts the test tube holder vertically or at a nearly vertical angle by magnetic attraction force generated by a magnetic coil.
For example, a cleaning liquid distributor in a cleaning centrifuge has been disclosed in JP-S50-022693-A. This distributor is characterized by including a container of which the inner surface is conical and nozzles arranged radially from a periphery of a bottom of the container, distributing equally the cleaning liquid injected from the center of the cleaning liquid distributor rotating together with the rotor upon application of the centrifugal force, and supplying the cleaning liquid from the nozzles into many test tubes held by the test tube holders.
Further, a technology of supplying cleaning liquid from a hole drilled in a cleaning liquid distributor that rotates together with a rotor into a test tube in a test tube holder supported so as to be pivotally movable by a rotor has been disclosed in JP-UM-H02-081640-A. Further, in JP-UM-H02-081640-A, it has been also disclosed that the rotor holds the test tube holder by a magnetic element
Further, a technology of rotating a rotor at a low speed while holding a test tube holder on a rotor by a rim or a rotary member at a small angle from a vertical direction thereby to discharge a supernatant of cleaning liquid from a test tube has been disclosed in JP-S48-027267-B and JP-S60-150857-A. Further, a technology of holding a test tube holder on a rotor by a magnetic element at a smaller angle from a vertical direction and of rotating the rotor at a low speed thereby to discharge a supernatant of cleaning liquid from a test tube held by the test tube holder has been disclosed in JP-UM-S54-167860-A.
On the other hand, in the bio cell cleaning centrifuge, an automatic blood cell cleaning centrifuge has been known, which executes automatically in turn a cleaning liquid injection step, a centrifugal step, a supernatant discharging step, and an agitate step which are included in a cleaning process. For example, an automatic blood cell cleaning centrifuge has been sold as a product name “himac MC450” by Hitachi Koki Co., Ltd. FIG. 8 shows, in such the conventional automatic bio cell cleaning centrifuge, a time chart for executing a cleaning process performed for the purpose of blood transfusion test. This time chart relates to rotation of a rotor drive motor, an operation of a pump of a cleaning liquid distributor, and energization to a magnetic coil of a magnetic element for fixing a test tube holder. A cleaning process using the conventional automatic blood cell cleaning centrifuge is executed as follows.
(1) First, in the cleaning liquid injection step at time (1) shown in FIG. 8, a test tube in which bio cell such blood cell has put is set in a test tube holder on a rotor, a motor for driving the rotor is rotated in an accelerative way, its centrifugal force moves pivotally the lower part of the test tube in the test tube holder outward, and the rotor (motor) is rotated in a state where the test tube is inclined at a predetermined angle to the horizontal direction from the vertical direction. At this time, as shown in FIG. 8, at the time (1), by putting the pump operation into an ON-state (a state where electric power is supplied to a pump), cleaning liquid is injected into the test tube through a cleaning liquid distributor which rotates together with the rotation of the rotor. The blood cell is stirred by the vigor of the injected cleaning liquid and cleaned.
(2) Next, in the centrifugal step at time (2) shown in FIG. 8, the rotor (motor) is centrifuged, for example, at 3000 rpm for 45 seconds. Hereby, the blood cell is deposited at the bottom of the test tube and an undesired substance such as a blood serum remains in a supernatant state.
(3) Further, in the supernatant discharging step at time (3) shown in FIG. 8, by putting the power supply to the magnetic coil in an ON state and putting the operation of the magnetic element into an ON state, the test tube holder is attracted in a nearly vertically state and fixed by the attractive force produced in the magnetic element. When the rotor is rotated again at a low speed, for example, at 400 rpm under this state, the test tube is directed such that its upper end is opened at a small angle or directed in the vertical direction. Therefore, the supernatant rises on the wall surface of the test tube because of the application of centrifugal force and then is discharged out of the test tube. When the rotation of the rotor is immediately stopped, only the deposited blood cell remains in the test tube.
(4) Next, in the agitate step at time (4) shown in FIG. 8, by repeating rotation and stop of the rotor gradually by turns, or repeating forward rotation and reverse rotation of the rotor gradually by turns, agitation is given to the test tube in the test tube holder on the rotor, thereby to loosen the blood cell deposited and solidified at the bottom of the test tube.
Cleaning is executed by usually repeating this cleaning cycle including the above four steps three to four times.
In JP-2003-337088-A, a bio cell cleaning rotor has been disclosed, which includes a cleaning liquid distributor used in a bio cell cleaning centrifuge for executing the above cleaning process, and a rotor around which test tube holders for holding plural test tubes to which cleaning liquid are supplied from the cleaning liquid distributor are attached in a circular array. FIGS. 9, 10 and 11 show the structure of the bio cell cleaning rotor which has been disposed in JP-2003-337088-A and includes the cleaning liquid distributor and the rotor which are generally used.
As shown in FIG. 9, a bio cell cleaning rotor 25 includes a rotor 2; plural test tube holders 3 which are attached onto the rotor 2 in a circular array so as to be pivotally movable around a pivot axis 3a, and pivotally moves toward a horizontal direction outside the circular array upon application of centrifugal force generated by the rotation of the rotor 2; and a cleaning liquid distributor 5 which is attached to the rotor 2, rotates together with the rotor, and supplies cleaning liquid to plural test tubes 4 held respectively by the plural test tube holders 3. As shown in FIGS. 10 and 11, the test tube holder 3 is characterized by holding the test tube 4 in a vertical state so that a center axis 4a of the held test tube 4 coincides with a vertical line direction 4y along a rotation axis 8a of the rotor 2.
In case that the above-mentioned cleaning liquid injection step is executed using such the bio cell cleaning rotor 25, as shown in FIG. 12, the test tube holder 3, without moving pivotally in the rotational direction or in the tangent direction of the circular array, moves pivotally in a horizontal direction outside the circular array because of the application of the centrifugal force generated by rotation of the bio cell cleaning rotor 25 thereto, and cleaning liquid 5a is injected in the test tube 4 to clean the bio cell. Further, in the supernatant discharging step after the above cleaning liquid injection step, as shown in FIG. 13, the test tube holder 3 is fixed by the magnetic element in a vertical state or in a nearly vertical state, and the supernatant is discharged while the test tube 4 is being held in the vertical state by the test tube holder 3 so that the center axis 4a of the test tube 4 coincides with the vertical line direction 4y along the rotation axis 8a of the rotor 2.
However, in the bio cell cleaning centrifuge provided with the above conventional bio cell cleaning rotor, it was not enough to suppress unevenness in amount of the cleaning liquid injected in the cleaning liquid injection step and unevenness in amount of the supernatant remaining in the supernatant discharge step.
In order to perform a good blood transfusion test by a centrifuge for automatic bio cell cleaning, it is desirable that: (1) the equal amount of the cleaning liquid is supplied to each of the plural test tubes held by the test tube holders by the cleaning liquid distributor in the cleaning liquid injection step; and (2) the equal amount of supernatant of the cleaning liquid is discharged enough from each of the plural test tubes in the supernatant discharge step.
Namely, in case that there is unevenness in amount of the cleaning liquid supplied in the many test tubes, for example, in case that the supplied amount of the cleaning liquid in one test tube is smaller than the supplied amount of the cleaning liquid in each of the remaining test tubes, bio cell in its one test tube becomes a sample in which greater amount of foreign objects such as antibodies remain in a suspension. To the contrary, in one test tube in which the supplied amount of the cleaning liquid is greater, the amount of the residual foreign objects such as the antibodies in its one test tube is smaller. This difference in residual amount of the foreign objects varies results of a reagent reaction test performed after the cleaning process using the bio cell cleaning centrifuge, so that the difference causes a serious error in judgment of the blood transfusion test.
Further, in case that the cleaning liquid is supplied from the cleaning liquid distributor on the basis of the test tube in which the supplied amount of the cleaning liquid may be small, in a test tube in which the comparatively great amount of the cleaning liquid is injected from the cleaning liquid distributor due to the unevenness in amount of the injected cleaning liquid, the cleaning liquid overflows from its test tube, which causes a problem that a valuable bio cell sample is lost. Further, in case that cleaning frequencies are determined based on the test tube having the small amount of the cleaning liquid, a disadvantage that a long time is required in the cleaning process is caused.
On investigation of the above conventional bio cell cleaning rotor, the present inventor has founded that the unevenness in amount of the cleaning liquid supplied into the respective test tubes occurs by several reasons. One of the reasons is that: since a distance between a cleaning liquid outlet of the conventional cleaning liquid distributor and an opening of the test tube is long, a part of the cleaning liquid injected from the cleaning liquid distributor cannot enter the test tube due to an error in working accuracy of the cleaning liquid outlet hole of the cleaning liquid distributor.
On the other hand, in the supernatant discharging step sequential to the cleaning liquid injection step, in case that the supernatant of the cleaning liquid are discharged from the many test tubes, unevenness in amount of the supernatant discharged from the many test tubes causes also an error in the test result. For example, in a test tube in which the amount of discharged supernatant is smaller, greater amount of the foreign objects such as the antibodies remain in its test tube after the supernatant discharge step. To the contrary, in a test tube in which the amount of discharged supernatant is greater, the amount of the residual foreign objects such as the antibodies in its test tube is smaller. This difference also varies the results of the reagent reaction test subsequently performed by the bio cell cleaning centrifuge, so that the difference causes an error in judgment of the blood transfusion test.
Further, in case that the processing time in the supernatant discharge step is prolonged or the rotation number in the supernatant discharge step is increased on the basis of the test tube in which the amount of the discharged supernatant is small, in the test tube in which the amount of discharged supernatant is greater, even the separated bio cells are discharged out of the test tube, so that a disadvantage that a valuable bio cell sample is lost can occur.